This invention relates to electrochemical cells and more particularly to electrodes for electrochemical cells.
In the nickel-cadmium alkaline cell, porous nickel plates are used to construct both the positive and negative electrodes. The active material for the positive and negative electrodes is contained within the nickel plates. The positive plate contains nickel hydroxide while the negative plate contains cadmium hydroxide.
U.S. Pat. No. 4,215,190 entitled "Light Weight Battery Electrode," issued to William A. Ferrando and Raymond A. Sutula on July 29, 1980, discloses an electrode grid comprising a sintered mat or felt of graphite fibers which are coated with a mixture of nickel and phosphorous. The electrode grid is strong, lightweight, and has good electrical performance. However, the nickel coated graphite fibers of the grid can be damaged when subject to pressures such as occur in convention paste loading procedures of active material. Moreover, when an active material paste is applied to the sintered plaque, severe blockage of the surface pores results. The great bulk of the paste remains outside of the plaque as surface layer. As a result, a method such as (1) a vacuum impregnation (polarization) process, (2) a thermal decomposition process, or (3) an electrochemical deposition process is used. These methods all have common features. In each, the impregnating solution is an aqueous nickel salt solution, usually nickel nitrate. Depending upon the method, the nitrate solution is electrolytically deposited within the pores and/or converted to the active nickel hydroxide form by the same means. The entire process requires tanks, counterelectrodes, power supplies and other equipment. It requires thorough rinsing of the electrode at various stages. The processes are suited to batch rather than continuous processing. The time required for all these operations is considerable. The total processing cost is correspondingly high.